Abrasive product



substantial proportion of Patented June 8,

No mowing.

This invention relates to abrasive productscoated abrasive products such as abrasive cecer and cloth and set-up Wheels.

This application is c coritiouutlomio-pert oi my copeuding applications, Serial No. 93,938, filed July 27, 1938 and Serial No. 361,981, filed October 30, 1939.

An object oi the invention is the provision of improved abrasive articles including on improved binder. Another object of the invention is to provide 2. coated ubresive article contsiuiug a. binder which includes as an essentiel ingredient a synthetic gum which can be token up in Water end consequently can be substituted for glue in the ordinary sandpaper machinery. Another obiect of the invention is the provision of improved binders for coated abrasives comprising a. suit of an ethenoid resin. (Ether objects will appear from a; consideration oi the description of the invention as hereinafter set forth.

The etherioici resins employed in my invention are those formed by the polymerization of compounds containing .9. doublehmided carbon atom, there being always included in the polymer a. substantial proportion of e. compouuol which contains s. neutralized organic acid group. Examples of ethenold resins which are cepohle of forming salts by ueutraliretion with ollrslis and are therefore useful in my invention are the oolyscrylic acids; lieteropolymers of vinyl or acrylic compounds with oieflrlic acids, and partial vinyl esters of poly'ousic acids which contain free acid groups.

Allrslis which may oe employed to form, with the acid-containing ethenolcl resins, the salts which are used in my invention include the inorganic bases such as sodium. potsssi sud ammonia, and organic losses such es dlor triethonol amine, the emyl smirlcs sud pyridine. It will thus be seen that there are three specific classes of ethenoid resins which meet the requirements of my improved hinder. A common characteristic of the etheuoiol resins which are neutralized to form as salt is the presence of a tree organic acid groups in polymers formed irom a ty o1 unsaturated monomers containing ethylene linkussive rouc'r f hie, Niagara F, N. Y., assiglnor to d Company, Ni N. L a commotion oi lee Application luugust 17, 1940. Serial No. 353.4965

A r at FMHS,

iii

ages. any of the salts, and particularly those formed with water-soluble inorganic buses or amines, are water-soluble. In one case the hinders comprise the salts of polymers of an acrylic acid. In the second case. esters are iormed by reacting only o part of the carboxyl groups appearing in the monomer with polyvinyl alcohol sud-neutralizing. additional carleoxyl groups with alkali to form salts. The third class includes the suits of heteropolymers in which the double bond of an ethenoid linkage is opened up to join a. vnyl or acrylic com- Eli pound containing so cold group and provide a polymer containing organic sold groups in the.

chain, these latter groups being neutralized with the alkali to form the salt.

fipecific compouudsof the first class, the salts of which have been found to be suitable in cerrying out my invention include polyecryllc acid and poiyclpha-methacrylic sold. As is known, compounds of this class can be polymerized by subjecting the monomeric compounds to suitable treatment such as by ecsure to ultra. violet light or heating or by the employment of a suiteble catalyst such as oxidizing agents like hydrogen peroxide.

The second group of compounds suitable for my purposes comprises certain polyvinyl esters of polybusic acids in which only port of the acids are esterified, thus leaving uucombined acid groups which are neutralized. In describing and claiming such esters, I have chosen to refer to such compounds, in which only part of the acid groups-in the polyocsic acid are esterified, as "partial polyvinyl esters. For example, c. polyvinyl ester oi a monobcsic acid, such as poly the sulphonic cold (503K) group. The products,

obtained have widely varying properties depending upon many factors such as the molecular weight of the original polyvinyl acetate, the proportional cud type or polybasic acid used, and the time, temperature, solvents and catalysts used intlie reaction.

I my also employ the salts of couolymers and heteropolymers of these partial polyvinyl esters of polybasic acids. These may be produced by partial reaction. by partial hydrolysis or by using copolymers and heteropolymers or their components as the raw materials for the production of copolymers and heteropolymers of partial polyvinyl esters of polybasic acids. Still another method of preparing these salts of partial esters is to esterify polyvinyl alcohol with polybasic acids, their anhydrides or their chlorides and neutralize the esters with alkali. It is thus evident that several methods of attaching acid groups to the polyvinyl compound may be used.

The-third group comprises the salts of resins formed by the heteropolymerization of a compound containing a vinyl group with an oleiine carboxylic acid or a compound capable oi forming such an acid. Specific materials containin the vinyl group are styrene or vinyl benzene, and vinyl and acrylic acid esters such as vinyl acetate or chloride and methyl acrylate or methacrylate. Alternatively, the heteropolymers may be hydrolyzed to form heteropolymers of vinyl alcohol with the acids, or the heteropolymer may be preliminarily hydrolyzed and reacted with an aidehyde to form an acetal. Suitable olefine acids and derivatives include maleic, fumaric, crotonic, itaconic and citraconic acids and the anhydrides,

chlorides, nitriles and other derivatives capable of conversion to the corresponding acids.

The formation of the polymers may be induced by any of the conventional methods employed in polymerization as by heating, exposure to ultra yioilet light and the addition of suitable cata- In making abrasive coated products, a coating of liquid adhesive is applied to the backing'material, abrasive grains are distributed over the adhesive-coated surface, and the thus-coated article is treated to solidify the liquid adhesive. A

second coating of adhesive, usually called a "sizing coat, is commonly applied after the grains have beenattached by the first or fmaking" coat ofadhesive to provide additional binder for the grains. This sizing coat must also .be hardened.

In preparing the liquid adhesives used in my invention I first make up a polymer of the acid or acid-containing compound, preferably one having -a high molecular weight because such resins are tougher and make better binders, and.

I then dissolve the polymer in a solution of an alkali. *While sufficient alkali to neutralize all of the acid may be used, I have found that solutionsmay be prepared by using less alkali than -is needed to completely neutralize the acid and that both the liquid adhesives and the solidified binders thus prepared are eminently satisfactory for use in the invention.

I have also found that the invention can be carried out ,by starting with a polymerized derivative of an acid such as a nitrile or a chloride instead of the acid itself. In this modification of of which depend upon the composition of the solidlfledbinder obtained after the hardening treatment.

The adhesive coating and the abrasive grains ay be app ed by any of the m hods u ed in the manufacture of coated abrasive articles. For

example the adhesive may be applied by passing a moving web between a pair of rolls one of which is rotated while partially immersed in a vat of the liquid. Alternatively the adhesive maybebrushed 0r sprayed onto the backing.

The hardening treatment which is used to solidify and set up the liquid adhesive comprises as an essential step the removal of water. This step may be carried out in the manner commonly used in the manufacture of glue bonded sandpaper where the coated web is festooned and hung in drying chambers which causes evaporation of the water under controlled conditions.

While I havefound that articles bonded with these salts of polyacids or polymers containing acid groups are superior for many purposes, my invention includes other modifications or embodiments which constitute additional improvements over the prior art for some purposes, In this modification of the invention the salts of my invention are not used to form the entire binder for the abrasive grains but rather they are modified by the inclusion of other bonds which are compatible with them in both the liquid andthe final solid conditions. i

I have found that other kinds of binders which have been previously used in the-manufacture of abrasive articles may be substituted for a part of the salts which form the principal feature of .the invention. Examples of such binders are cellulose derivatives, such as cellulose esters and ethers, and heat hardenable resins as exemplified by phenol-formaldehyde condensation products.

The use of combinations of the salts with these other binders has a number of advantages. For example the salts of polyacrylic acids have been found to be excellent dispersing agents for promating and stabilizing aqueous dispersions of solutions of esters in organic solvents. Where they are so used the products serve the dual function of acting as a dispersing agent for the esters in the liquid state and plasticizers or modifiers for the esters when they are solidified and are functioning as a binder for the abrasive grains.

Cellulose esters such as cellulose nitrate or acetate have previously been suggested as binders for coated abrasives but min as applicant is aware they have not been used because it has been necessary to liquefy them by dissolving in organic solvents. These solvents are expensive, explosive, and otherwise undesirable. By dispersing the esters in water with the aid of salts of my invention. as the dispersing agent it is unnecessary to use much solvent because the esters can be made dispersible by.taking them up in a small amount of solvent and-then liquefied to the desired viscosity with water.

- As indicated the salts may also be blended with other types of resins to assistin liquefying the resins and to modify their properties when they in conjunction with the more inflexible resins as exemplified by the hardened phenolic resins. My invention has a number of advantagesover the articles of the prior art. Products made in ing sandpaper with glue binder.

accordance with the invention have been found to be superior to glue-bonded sandpaper for many all classes of work and it has not been possible to provide special bonds for special purposes as iscommonly done with abrasive wheels. By

utilizing different resins of my invention a binder can be prepared which is best adapted for each particular use to which the abrasive product-is to be applied.

While ,I have described my invention with particular reference to certain specific materials it is to be understood that the invention is not limited to the particular materials and methods herein referred to.

I claim:

' l. A coated abrasive article consisting of a I backing and a surface layer of abrasive'grains attached thereto by a binder comprising the water-soluble neutralization product of a water-' tion of organic acid groups.

unsaturated monomers including'an acrylic acid. 2. A coated abrasive article consisting of a backing having a surface layer of abrasive grains attached thereto by a binder comprising a salt of a polyacrylic acid. v 4

3. A coated abrasive article consisting of a backing having a surface layer of abrasive grains attached thereto by a. binder comprising a salt of polymethacrylic acid.

4. A coated abrasive article consisting of a backing having a surface layer of abrasive grains attached thereto by a binder consisting essentially of a 'salt of a polymerized acrylic acid and a cellulose derivative selected from the group consisting of cellulose esters and ethers.

' 5. A coated abrasive article consisting of a backing having a surface layer of abrasive grains attached thereto by a binder consisting essentially of a salt of a polymerized acrylic acid and a heat hardened condensation product resin.

6. A coated abrasive article consisting of a backing having a surface layer of abrasive grains attached thereto by a binder consisting essentially of a salt of a polymerized acrylic acid and a heat hardened phenolic condensation product.

7. An abrasive article comprising abrasive grains and a binder therefor comprising the neutralization. product of an alkali with an ethenoid resin containing aisubstantial proper;

NQRMAN P. 303m.

soluble alkali and a polymer of a plurality of I 

